In U.S. Provisional Patent Applications Nos. 61/107,112 (7865-373) filed Oct. 21, 2008, 61/193,457 (7865-374) filed Dec. 2, 2008, 61/202,070 (7865-376) filed Jan. 26, 2009, 60/202,553 filed Mar. 12, 2009 (7865-383), 61/213,717 (7865-389) filed Jul. 7, 2009, 61/272,241 (7865-400) filed Sep. 3, 2009 and U.S. patent application Ser. No. 12/603,087 (7865-415) filed Oct. 21, 2009 (US Patent Publication No. 2010-0098818), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described the preparation of a soy protein product, preferably a soy protein isolate, which is completely soluble at low pH values and is capable of providing transparent and heat stable solutions at such low pH values. This soy protein product may be used for protein fortification of, in particular, soft drinks and sports drinks, as well as other acidic aqueous systems, without precipitation of protein. The soy protein product is produced by extracting a soy protein source with aqueous calcium chloride solution at natural pH, optionally diluting the resulting aqueous soy protein solution, adjusting the pH of the aqueous soy protein solution to a pH of about 1.5 to about 4.4, preferably about 2.0 to about 4.0, to produce an acidified clear soy protein solution, which may be optionally concentrated and/or diafiltered before drying.